linux-kernel - Re: [PATCH] docs/vm: add documentation of memory models

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Message-ID: <2b97f4db-78c0-1cad-bdf5-948720e8094f@infradead.org>
Date:   Thu, 25 Apr 2019 08:01:39 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] docs/vm: add documentation of memory models

On 4/25/19 1:22 AM, Mike Rapoport wrote:
> Hi Randy,
> 
> On Wed, Apr 24, 2019 at 06:08:46PM -0700, Randy Dunlap wrote:
>> On 4/24/19 3:28 AM, Mike Rapoport wrote:
>>> Describe what {FLAT,DISCONTIG,SPARSE}MEM are and how they manage to
>>> maintain pfn <-> struct page correspondence.
>>>
>>> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
>>> ---
>>>  Documentation/vm/index.rst        |   1 +
>>>  Documentation/vm/memory-model.rst | 171 ++++++++++++++++++++++++++++++++++++++
>>>  2 files changed, 172 insertions(+)
>>>  create mode 100644 Documentation/vm/memory-model.rst
>>>
>>
>> Hi Mike,
>> I have a few minor edits below...
> 
> I kinda expected those ;-)
> 
>>> diff --git a/Documentation/vm/memory-model.rst b/Documentation/vm/memory-model.rst
>>> new file mode 100644
>>> index 0000000..914c52a
>>> --- /dev/null
>>> +++ b/Documentation/vm/memory-model.rst
> 
> ...
> 
>>> +
>>> +With FLATMEM, the conversion between a PFN and the `struct page` is
>>> +straightforward: `PFN - ARCH_PFN_OFFSET` is an index to the
>>> +`mem_map` array.
>>> +
>>> +The `ARCH_PFN_OFFSET` defines the first page frame number for
>>> +systems that their physical memory does not start at 0.
>>
>> s/that/when/ ?  Seems awkward as is.
> 
> Yeah, it is awkward. How about
> 
> The `ARCH_PFN_OFFSET` defines the first page frame number for
> systems with physical memory starting at address different from 0.

OK.  Thanks.

>>> +
>>> +DISCONTIGMEM
>>> +============
>>> +
>>
>> thanks.
>> -- 
>> ~Randy
>>
> 


-- 
~Randy